Body Control Module: Description and Operation

BODY CONTROL MODULE (BCM)

The CTD system is an internal function of the body control module (BCM) which utilizes various switch input information to perform CTD functions. When the BCM detects an unauthorized entry, it activates the horns and exterior lamps. The BCM has 5 basic modes (disarmed, standby, delayed, armed, and alarm) for operating the CTD system. The different modes are described below.
1. The BCM has the CTD system in a disarmed mode until the following conditions are detected:
- Ignition key turned to the OFF position
- Any door open
- Doors locked by either the power door lock switch or the LOCK button on the transmitter
2. The BCM enters the standby mode when the above conditions are detected. In standby mode, the BCM commands the theft LED to flash quickly. If all the doors are closed and the LOCK button on the transmitter is used, the BCM enters the delayed mode.
3. When the last door is closed, the BCM enters the delayed mode for 30 seconds. In delayed mode the BCM commands the theft LED to illuminate ON steady.
4. After 30 seconds, the BCM enters the armed mode. In armed mode, the BCM commands the theft LED to flash slowly. Any forced entry activates the alarm mode.
5. When the BCM detects a forced entry, the BCM enters the alarm mode. The BCM activates the horns and exterior lamps for 30 seconds. This is followed by a 3 minute time-out with the horn no longer active. If no new intrusions are detected after the time-out, the horn is not active. The system must be disarmed or the intrusion condition removed after the time-out for the system to exit alarm mode.

The Body Control Module (BCM) controls the interior lamps illumination.

One of the following 3 BCM types are installed on the vehicle based upon the vehicle equipment:
- BCM type 2
This provides the interior illumination control, inadvertent load (battery rundown) protection, chime functions and automatic power door locks.
- BCM type 3
This provides BCM type 2 features plus the keyless entry system (RPO AUO).
- BCM type 4
This provides BCM type 2 and 3 features plus the content theft deterrent (RPO UA6) with remote activation verification and the remote alarm.

For more information regarding the BCM, refer to Body Control System.